JUNEAU, Alaska — An environmental audit of the Kensington Mine found the operation to be “generally in compliance” with conditions regarding its waste disposal and long-term closure plan, but auditors pointed out some long-term challenges for the gold mine.

Auditors hired by the mining company Coeur Alaska visited the gold mine last fall, KTOO Public Media of Juneau reported . The auditing firm HDR’s recommendations are outlined in a 60-page report.

Auditors found issue with exposed rock that when mixed with air and water can create sulfuric acid. KTOO Public Media compared the problem to metal rusting when left out in the rain.

“The audit is a critical for the agencies for taking a look — kind of a third party objective look — at our permitting program to see if there’s areas of improvement,” said Allan Nakanishi, an engineer with the Department of Environmental Conservation overseeing waste disposal at the mine. “It’s not uncommon in the Southeast to hit pockets of material that have high sulfide minerals within it and that go acid.”

In response to the audit, the mining company said areas of concern are limited to the tailings treatment facility. The company said it’s working to engineer a solution.

But mine critics say acidic runoff threatens water quality in the long run.

“You know, once acid generation starts, it’s almost impossible to stop it and it’s very obvious even through the pictures that it’s getting worse over time,” said Guy Archibald, staff scientist for the Southeast Alaska Conservation Council.

The Department of Environmental Conservation cited the mine in 2013 for acid runoff leeching into its unlined tailing treatment facility, prompting quarterly samples to be taken at the facility.

The auditors recommended the state begin monitoring the flow of contaminated water to keep tabs on that situation. They also gave mixed reviews to the effectiveness of concrete applied to seal off the source of the acid runoff.

“Some of the recommendations, I think, are valid and warranted,” Nakanishi said, “and we will be using this audit in the development of the future permit.”

Information from: KTOO-FM, http://www.ktoo.org